Lower et al Pat. No. 4,802,591, titled "Louvered Chip Screener" discloses a machine and method for separating chip-like particles according to thickness, wherein the deck of the machine comprises a series of spaced flexible "louvers" or slats which extend parallel to the direction of chip flow on the deck. The slats are canted (tilted) transversely to the direction of the flow and present elongated slot-like chip openings between them. The slats are supported in a frame by a series of pedestals or posts mounted on cross-members in the frame. The pedestals have bases which are secured on the cross-members, and upstanding legs or backs with angulated tops onto which the slats are secured. Screening machines of the "louver" type are especially useful because they provide low blinding and high efficiency at high throughput in sustained screening use.
In practice, however, it has been found relatively difficult to precisely align the pedestals on the cross-members so that the width of slots between slats secured on the angulated tops is as uniform as might be desired. For example, in one chip screener it is desirable to maintain a width tolerance of no more than 0.5 mm in a nominal 9 mm slot. The slot width determines the maximum thickness of the chips which fall through; variation in slot width from slot to slot, or along the length of a given slot, blurs the separation of the fractions. One major cause of non-uniformity of slot width is variation in pedestal position and alignment. Such screen decks usually have a welded aluminum frame, and in practice the frame members often "bow" somewhat so that the pedestal bases do not all lie in a common plane, as a result of which the pedestals are not in straight rows. Further, it is difficult to secure the pedestal bases to the cross members in precise positions (for example as by riveting). Slight mis-spacings, non-planarity or "cocking" of pedestals are reflected as variations in slot width.
Thus, there has been a need for a better means of positioning and mounting the slats of slat-type screeners.